When a projectile travels through a fluid (e.g., atmospheric air) during flight, the projectile will experience drag forces that act on the projectile as it travels through the fluid. Types of aerodynamic drag that generally act on a projectile during flight are wave drag (e.g., the drag force resulting from aerodynamic shock waves), skin friction drag (e.g., the friction between the airstream and the surface of the projectile), and base drag (e.g., a vacuum effect at the back of the projectile). These aerodynamic drag forces will reduce the speed of the projectile. For example, in the case of a non-self-propelled projectile, drag will reduce the range and accuracy of the projectile as the drag forces act against the initial energy imparted to the projectile. By way of further example, a significant, and uncontrollable, source of error in the accuracy of a projectile, such as a long-range sniper round, is drag forces that cause the projectile velocity to decrease, which increases the time of flight to a target and also increases the likelihood of the projectile deviating from its intended course during flight. In the case of self-propelled projectiles, drag may reduce the accuracy of the projectile and requires more power to propel the projectile during flight.
With aerodynamic drag forces and, in particular, skin friction drag, the total friction to movement of a body through a gas (e.g., atmospheric air) for a given Reynolds number (Re) depends largely upon the aerodynamic design of the particular body concerned. On a projectile, it is generally desirable to delay the transition from laminar to turbulent airflow along the surface of the projectile as much as possible. At moderate speeds, it may be possible to reduce the amount of turbulent flow by proper aerodynamic design of the projectile. However, at relatively higher speeds, turbulent flow invariably results, with the attendant disadvantages of a sudden increase in drag and decrease in lift that will reduce the accuracy of the projectile. Such effects ultimately reduce the distance the projectile is able to travel, given the initial energy imparted to the projectile, and reduce the overall accuracy of the projectile.
One attempt to reduce sonic waves and aerodynamic drag on an airframe of an aircraft is disclosed in U.S. Pat. No. 3,446,464 to William A. Donald, issued May 27, 1969, the disclosure of which is hereby incorporated herein in its entirety by this reference. As disclosed therein, one or more forward electrodes are applied adjacent the leading edge of a wing or other aerodynamic surface of an aircraft and rearward electrodes are provided on the wing or other aerodynamic surface at a position trailing the leading edge to establish an electric field between the electrodes. The strength and direction of the electric field formed between the electrodes are selected to exert a force on air particles in the electric field leading the air particles from the vicinity of the forward electrodes toward the rearward electrodes. This movement of air particles reduces the buildup of air pressure in front of the leading edge of the wing of the aircraft that results in sonic waves and aerodynamic drag.
Another attempt including projecting electrodes for use with self-propelled vehicles, such as aircraft and space craft, is disclosed in U.S. Pat. No. 2,949,550 to T. T. Brown, issued Aug. 16, 1960, the disclosure of which is hereby incorporated herein in its entirety by this reference.
However, such configurations including electrodes extending from the leading end of an airfoil or other surface of an aircraft or vehicle may not be applicable to other devices that travel through a fluid during flight, such as projectiles, which may be substantially smaller in size and of far different configuration than surfaces of an aircraft. Further, the electronic components disclosed in U.S. Pat. Nos. 2,949,550 and 3,446,464, which are used to create the electric field, may not be applicable to other devices that travel through a fluid during flight.